Insecticide@Silica Nanocontainers with High Cypermethrin Load and Improved Photostability

Cypermethrin (CM) is a widely used insecticide to repel and control stinging, biting and sucking‐licking insects. To limit the required CM amount, to reduce application cycles, and to increase its stability, we developed CM@OS core@shell nanocontainers (OS: n ‐octylsilicate) as a novel synthesis concept and material. The CM@OS core@shell nanocontainers are synthesized via a solvent/antisolvent approach. They exhibit a mean total diameter of 34 ± 8 nm with a CM particle core of 15 ± 3 nm in diameter and an OS particle shell of 7 ± 2 nm in thickness. Due to negative surface charging (–63 ± 1 mV), the as‐prepared nanocontainers are colloidally very stable as aqueous suspensions. Analytical characterization is performed by electron microscopy (SEM, TEM, STEM), electron spectroscopy (EDXS), and additional methods (DLS, zeta‐potential analysis, FT‐IR, TG, C/H/N/S analysis, photometry). The CM content is 10 wt‐%, and CM is photochemically significantly stabilized in regard of a cleavage of the ester group as well as of the cyclopropanyl ring in comparison to free CM. Thin‐films are realized, and the slow CM release exemplary shown, and promoted by the lipophilic functionality of OS.